The present invention relates to semiconductor spacer structures used in the fabrication of multi-chip modules, and to the manufacturing method of such packages.
To obtain the maximum function and efficiency from the minimum package, various types of increased density packages have been developed. Among these various types of packages is the so-called multi-chip module, multi-chip package or stacked chip package. A multi-chip module includes one or more integrated circuit semiconductor chips, often referred to as circuit die, stacked one onto another to provide the advantages of light weight, high density, and enhanced electrical performance. The multi-chip packages may contain all circuit die or a mixture of circuit die and spacer die, the spacer die typically being used to separate circuit die.
Semiconductor chip packaging process typically begins with wafer dicing, that is, sawing a semiconductor wafer to separate the wafer into individual semiconductor devices or chips. Before sawing, a wafer mounting tape is typically attached to the backside of the wafer. The wafer mounting tape keeps the chips together after the sawing.
The semiconductor chip is typically adhered to a previously mounted chip or to the substrate with a paste (typically an epoxy paste adhesive) or a film adhesive. Generally, paste adhesives have been used more often than film adhesives. However, some multi-chip modules are more successfully fabricated using film adhesives because the thickness of adhesive film is uniform so that there is minimal or no tilt of the semiconductor chips and no fillet of adhesive encircling the semiconductor chip. Moreover, no resin is bled so that it is suitable for multi chip stacking and packages with tight design tolerances or thinner chip.
In one method of fabricating a multi-chip module using film adhesive, an adhesive film is laminated directly to the backside of the semiconductor wafer and then the wafer is diced into individual semiconductor chips using conventional wafer dicing equipment. For stacking the semiconductor chips, each chip is lifted by a chip-bonding tool, which is usually mounted at the end of a pick-and-place device, and mounted onto the substrate or onto a semiconductor chip mounted previously. This method requires special film laminating equipment. However, it can shorten fabrication time and lower cost because the paste-dispensing process is not needed.
After the chip mounting process, bonding pads of the chips are connected to bonding pads of the substrate with Au or Al wires during a wire bonding process to create an array of semiconductor chip devices. Finally, the semiconductor chips and their associated wires connected to the substrate are encapsulated, typically using an epoxy-molding compound, to create an array of encapsulated semiconductor devices. The molding compound protects the semiconductor devices from the external environment, such as physical shock and humidity. After encapsulation, the encapsulated devices are separated, typically using a laser saw, into individual semiconductor chip packages.